The invention relates to a torsion spring clutch, in particular for recording and/or playback equipment, comprising two clutch sections, which are coaxial with and rotatable relative to each other, and a helical torsion spring, which is slid onto the two clutch sections for the transmission of force between said sections. Such a torsion spring clutch is for example known from U.S. Pat. No. 3,085,758.
In such a torsion spring clutch the first clutch sections is rigidly connected to the torsion spring and the second clutch section is in frictional engagement with the torsion spring, whose turns have been slid onto said clutch section with a specific pretension. The pretension in the turns of the torsion spring is obtained by selecting the diameters of the torsion spring and the clutch section so that the turns of the torsion spring are widened when the spring is slid onto the clutch section, the resulting increase in diameter of the individual turns of the torsion spring determining the pretension in these turns. If during operation of the torsion spring clutch its direction of rotation is selected so as to oppose the winding direction of the helically wound torsion spring, the torsion spring is tightened onto second the clutch section which it frictionally engages, which results in a substantially rigid coupling between the two clutch sections via the torsion spring. However, if the direction of rotation of the torsion spring clutch corresponds to the winding direction of the torsion spring, a torque which is proportional to the maximum value of the pretension can be transmitted between the torsion spring and the second clutch section. When the maximum torque that can be transmitted between the torsion spring and the second clutch section is exceeded, slip occurs, the drive connection between the clutch sections then being disengaged. When such torsion spring clutches are used it is frequently required to adjust the value of the maximum torque that can be transmitted. This is for example the case when the torsion spring clutch serves for driving a winding hub or a drive wheel in recording and/or playback apparatus.